How much attic insulation do I need?

Measure current depth in several places, air seal first, then add to the level recommended for your climate zone. Coverage consistency matters as much as the headline depth.

Last reviewed 2026-07-15

Thin, patchy or displaced insulation is far more common than uniformly inadequate insulation, and the eaves are usually the worst area.

Adding depth over an unsealed attic floor reduces the benefit and makes future air sealing much harder, so sequence matters.

What to check first

  • Depth measured at several points, including near the eaves
  • Whether soffit baffles are present and vents are clear
  • Damp, compressed or displaced material, which indicates another problem
  • Required clearances at flues, chimneys and non-rated recessed fixtures

When to call a professional

  • Vermiculite or suspected asbestos-containing material is present — do not disturb it
  • There is active moisture, mould or a roof leak
  • Knob-and-tube wiring runs through the area